Sudden Power Issue - Vintage Mustang Forums
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post #1 of 8 (permalink) Old 09-02-2019, 03:34 PM Thread Starter
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Sudden Power Issue

Recently moved from California to Florida with my 68 Mustang. First two months the car ran great. Then one day (while driving) the engine started running very erratically. Was throwing out studdering Power, even at constant throttle. Then died all together when I clutched for a red light. Was able to limp it home by feathering the throttle. Dove into it a little bit, but haven’t had success so far. Did notice that the engine is now running very rich, and the plugs indicate it with a lot of soot. I did a cylinder compression test with the engine cold and all looks good. I did notice some external arcing on the msd 3 ignition coil and noticed the top of the coil was loose. Replaced the coil and it didn’t fix it. With the suddenness this happened, my guy is telling me it’s an ignition or compression problem. Still have to inspect the plug wires and do a warm engine cylinder press check. Anyone have any common actors that cause my ride to suddenly do this? Car has a 302 with Holley 4 barrel carb. Has an MSD 6AL ignition box with electronic distributor. Getting frustrated with my ride broke in my garage. Any tips?
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post #2 of 8 (permalink) Old 09-02-2019, 03:40 PM
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Have a look at the carb. Is the choke staying shut? When an electric choke fails it fails closed. Don't know if you have a manual or electric, but seems everyone has electric nowadays. Shutting off the air flow lines up with your running rich observation. And electric chokes can fail suddenly. Power connection breaks or it just dies.

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post #3 of 8 (permalink) Old 09-02-2019, 08:20 PM
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Originally Posted by CannedCrev View Post
Did notice that the engine is now running very rich, and the plugs indicate it with a lot of soot.
Sounds like it's running rich all of a sudden. Besides the choke, could be a carb float valve has stuck open. Check the fuel level in the carburetor.
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post #4 of 8 (permalink) Old 09-02-2019, 09:08 PM
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While this may not be your immediate problem, keep in mind that plug wires that are wearing out in California will behave badly in Florida once the humidity settles in.
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post #5 of 8 (permalink) Old 09-07-2019, 08:42 PM Thread Starter
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Thank you all for the advice. My choke is working as advertised and my plug wires are good. Think I found the problem. I noticed that the secondary nozzles were constantly dripping fuel while the engine was idling, and then they continued to drip after the engine was turned off. Took out the sight plug for the secondary float, and fuel came running out. Adjusted the float and the dripping stopped. Rich smell went away and she started running normal again. However, I might have a new problem. First off I tore the seals for the float adjustment while messing with it, so I will have to replace them. The fuel level in the secondary bowl is now too low. It should be just below the sight hole, but it is well below. However, the float adjustment doesn't seem to do anything to the fuel level. I turned the adjustment nut five whole turns counter clockwise (per the manual) to raise the fuel level, but it didn't do anything. Are the floats easy to break? I have a Holley 4160.
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post #6 of 8 (permalink) Old 09-07-2019, 09:27 PM
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Spring for a gasket kit and pull the float bowl. Replace the needle and seat as well as the adjusting screw gasket.


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post #7 of 8 (permalink) Old 09-07-2019, 09:54 PM
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Originally Posted by Woodchuck View Post
Spring for a gasket kit and pull the float bowl. Replace the needle and seat as well as the adjusting screw gasket.
Agree, but it's probably just trash in the needle valve. You shouldn't normally have to adjust the float level, although here in humid, old Florida, frequent mixture adjustments are needed. Very common on these carbs, especially cars that are driven less frequently. Drop in a new needle and seat with new lock and adjusting screw gaskets, and you'll be good ta' go!

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post #8 of 8 (permalink) Old 09-09-2019, 11:03 AM
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The harsh chemicals in fuels today seem to eat the seals on the needles/seats. You might want to replace those.

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